Solid-state drives (SSDs) have been developed as data storage apparatuses, each using NAND flash memories (hereinafter referred to as NAND memories in some cases) that are rewritable nonvolatile memories. Data storage apparatuses for use in servers or enterprises, in particular, are implemented by SSDs of large storage capacity.
In most high-speed IC memories, the timing of a strobe for latching data must be adjusted. (This adjustment is called calibration.) NAND memories operate at a relatively low speed. Nonetheless, the calibration must be performed on the NAND memories in order to provide an SSD having a large storage capacity. This is because many NAND memories are densely arranged in a single package, and the SSD is constituted by more and more packages. Ultimately, the interconnections run longer distances and the overall load increases, inevitably deforming the waveform of signals.
The larger the storage capacity of an SSD, the greater the number of interface channels provided for the NAND memories. Therefore, the calibration should be performed on the channels at high speed in order to manufacture an SSD with higher efficiency.